Hydraulic brake



April 26, 1938 N. A. CHRIS HYDRAULIC TENSEN BRAKE Filed Dec. 29, 1933 -7fm e@ INVENTOR lV/ELS 0. Cv'f/e/reA/PA/ ATTORNEY Patented Apr. 26, 19382,115,383` vNiels A. Christensen. south Euclid, ohio ArrlicationDecember 29, mast-rial No.1n4,'fi63 y 1 claims; (creo-54.5) I j 'I'hisinvention relates to new and useful improvements in hydraulic brakes andmore particularly to an improved seal for the pistons of power conveyingcylinders.

An important object of the invention is to pro-v vide these sealsin theform of highly compressed elastic packing rings slidable with the pistonand on cylinder walls lubricated by the hydraulic brake fluid of thesystem to avoid such wear as would be expected in subjecting the ringsto a sliding action. i

Another object of the invention is .to provide a power conveyingcylinderwhich will automatically compensate for any loss of liquid inthe system upon return strokes of the piston.

A further object of the invention is to .provide a simple, inexpensiveand easily assembled construction which will outlive the usual cupsemployed heretofore. l

Other objects and advantages of the invention will become apparent`during the course of the following description.

In the accompanying drawing forming a part of the description andwherein like numerals are employed to designate like parts throughoutthe several views,

Fig. 1 is a longitudinal section of the improved power conveyingcylinder,

Fig. 2 is a fragmentary transverse section of the same taken on the line2-2 of Fig. 1,

Fig. 3 is an enlarged section of the improved packing ring prior toassembly,

Fig. 4 is an enlarged fragmentary longitudinal section of a portion of apower conveying cylinder illustrating the packing ringin operativecompressed condition. y

Figs. 5 to 7 Ainclusive are views of modified forms of power conveyingcylinders.

Referring now more particularly to the drawing for a more detailedexplanation of the principle of the invention, the numeral 5 designatesthe main casing of a power conveying cylinder formed with an open topwhich is closed by a removable cover Shaving a suitable threaded andflanged opening 1 for the insertion of a filling and vent plug, notshown. The casing is formed with an integral barrel or cylinder portion8, the forward end of which is provided with threaded nipple aperturesor ports 9 and I0 for the attachment of pipes or conduits, one leadingto other power conveying cylinders of thefront wheel brakes of thevehicle and the other to the rear wheel brake mechanisms to createpressure therein by which the front and rear brakes are applied.

by providing arestricted annular portA I1 'form-` v` ing means ofcommunication between the interior of the barrel 8 and the space betweenthe same and the cover 6 which forms an Oil reservoir I8.v This cylinderforms a `continuation of bar-rei 8. A plurality of circumferentiallyspaced openings I9 are provided in the cylinder I4 -rearwardly of portsI1-to always communicate the reservoir with the annular space` 20 formedbetween cylinder I 4 and the reduced mid-section 20 2| of areciprocatory piston 22 slidably received within the cylinder Il andbarrel 8.

A gasket 23 is positioned between the rear end II of the casing and thelateral flange I5 of cylinder I4 to provide a liquid seal and also maybe used in varying thicknesses to vary the width of the annular port I1.Secured to the outer face of lateral fiange I5 by means of screws I6, isa metal stop disc 24 having a central opening surrounded with a turnedback flangev 25, forming a groove into which fits one end of an lelasticboot 26. The outer end of this boot is fitted within an annular grooveof the socket end 21 of a piston stem 28 to exclude, extraneous matterfrom the piston and cylinder. socket receives a threaded shank which maybe. connected tothe usual brake pedal of a motor ve hile or any otherform of actuating mechanism.

' The `inner end 29 of the piston stem is semispherical to fit within acorrespondingcavity 30` in the piston 22. This cavity 30 is of somewhatconical form 'so that the stem has, in effect, a universal connectionvwith the pistonvwhereby axial thrust can be exerted on the pistonregardless of angularity of its stem.`

'I'he forward end or working face of piston .22 u;

within the annular flange Il is provided with an annular raised valveseat upon which seats a flat floating valve plate I4. This valve plateis non-circular and preferably square with a diagonal equal to the innerdiameter of flange 3l whereby the corners of the valve plate slidablyengage the inner surface of this flange and maintain the samecentralised with respect to an axial port :s extendingihmun the valveseat and communicatingv at its rear end with lthe annular space 2laround the piston by means of a plurality of lateral. radial ports Il.The outward movement of the valve 38 from its seat is limited bymeans ofa circular spring clip 31 seated in an ahead of the piston to replenishany oil which may have escaped from the system by leakage. Immediatelybehind this reduced forward end of the piston, the latter is providedwith an annular groove I! in which is received an elastic packing ringIl best seen in'Figs. A3 and 4. An identical groove Il and packing ringI2 is provided in the piston 22 further rearwardly from the forwardworking face of the piston than the first mentioned ring to serveas aseal or safety factor should the first mentioned ring ffail or leak dueto inferior or defective material. In Fig. 1 this second ring 42 ispositioned in a-groove located'rearwardly of the reduced intermediateportion of the piston, but if desired it'may be arranged closer to thefirst ring and forwardly of the reduced portion of the piston as 'shownin Fi 5.

hese packing rings are made ofsolid rubber or rubber composition verydense and yet possessive of great liveliness and compressibility. Aglyptal composition hasfbeen found extremely serviceable and resistantto wear andV leakage throughout kprolonged and severe tests. Each ringis perfectly circular and prior to assembly possesses circular crosssection as shown in Fig. 3. Its inner periphery is slightly less thanthe circumference of the piston under the groove while itsexteriorcircumference is greater than the inner circumference of the cylinder sothat when it is slid with the piston within the cylinder I4 andibarrel.l, the ring is compressed into substantially ellimoidal section as shownin Fig. 4. I have found in one embodiment of the invention that acircular section ring having a section diameter of 1'; of an inch servesadmirablyfor the purposes when it is compressed about of an inch wheninstalled thereby causing the normal circular section of the 'ring toflatten out to the extent of about of an inch on its opposite sides asindicated by the dimension line -A of Fig.y 4. In other words, the minordiameter of the section when installed is approximately' of an inchwhile its major diameter 'is approximately i', of an inch. y When inthis compressed condition within its respective groove, the latter isapproximately of an inch wider than the maior diameter of theellipsoidal form of the ring to thereby compel sliding as distinguishedfrom rolling movement ofthe ring during reciprocations of the piston. Aslight clearance bealiases tween the ring and one side of its groovepermits slight shifting of the ring relative to the piston, but notsufficient to permit twisting of the ring about its axis as would becaused by rolling action of the ring through 360 degrees. However l thissliding or partial rolling of the ring, as by the shifting of point B toE and C to F when the piston moves in the direction of arrow G, Fig. 4,kneads or works `the material of the ring to keep it alive and pliablewithout deleterious effects of scufllng which are caused by purelystatic sliding of rubber upon a surface. By this slight turning or`kneadlng action, the life of the ring is prolonged. When the pistonmoves in the direction of the arrow G, the ring 4l lI vwill be movedover 4against the right hand wall f of the groove, but when the pistonmoves in the direction of the arrow D, point E shifts to B and F to Cwhich ls a partial turn of the vring so that it is positioned backagainst the left hand wall ao of the groove and thereafter is caused toslide f l A along the wall of the barrel or cylinder. 'I'his causes thering to slightly roll across the fport ll and then slide after passingthe same.

Referring to Fig.. l, the piston is illustrated in its normal positionto release the brakes. In this position, hydraulic brake fluid from theres-r ervoir il enters the barrel 8 through port I1, vla space 3l toreplenish liquid in the system or lines. To apply the brakes by placingliquid in the system under pressure, the piston stem 2l is moved to theright of Fig. 1 under the action of the usual brake pedal or othermeans, thereby causing the piston 22-to move in a correspondingdirection.

'I'his causes the rings 40 and 42 to slide along the bores ofthecylinder il and barrel 8 respectively. The slightest forward movement ofthe piston causes ring l0 to move overrand close port l1 thereby cuttingoff flow of liquid from the res- A ervoir to the barrel. As soon as thepiston begins o its forward movement, the valve 34 is caused to close bythe constantly increasing pressure of liquid in the barrel 8. The liquidin the barrel is forced out through the ports 9 and l0 to theirrespective pipe lines to actuate brake applying mechanisms within thebrake drums. As the piston moves forwardly, pressure in the barrel lreacts through the space 38 and against the ring` 40 to further compressit against the piston and barrel walls to thereby further reduce thepossibility of leakage past the ring. This ring being in contact withthe brake liquid, and lubricatedcylinder walls, is always extremelyslippery to be freely slidable and minimize friction in spite of itshighly compressed condition. It possesses one very distinct advantageover the usual skirted cup and that is, it has no skirt which willcollapse and cause leakage upon retractile movement of the piston.

Upon the return stroke of thel piston 22 upon release of footr pedalpressure against the piston, the retractile spring 32 will expand toassist in moving the piston rearwardly so that the valve plate 34 willbe lifted from its seat by the rush of liquid coming from the reservoirIB to the port I9 and through the passages, 36 and 35 until the pistonreaches the limit of its return stroke determined by the abutment of theouter end of the piston with that portion of the plate 2l 70 which isbent for the reception of the inner end of the boot 26. Thispredetermined idle position of the piston automatically returns the ringl0 back beyond the port I1 so that whenever necessary, liquid may passfrom the reservoir I8 u into the barrel 8 in advance of the piston tocompensate for any leakage which may occur.

It will of course, be understood that instead of providing the packinggroove in the piston, it may be placed in the cylinder wall and thepacking ring placed therein, and the claims are to be construed ascovering this alternative construction.

I claim:

1. In a hydraulic brake system, a casing divided by an integral wallinto a reservoir and barrel, a cylinder extending through a wall of thecasing and in alignment with said barrel to form a continuation thereof,said barrel and cylinder being spaced apart to form a port therebetween,a piston'operating in said cylinder and barrel, and a packing ringcarried by the piston and arranged behind said port when the piston isin retracted position.

2. In a hydraulic brake system, a casing divided by an integral wallinto a reservoir and barrel, a cylinder extending through a wall o f thecasing and in alignment with said barrel to form a continuation thereof,said cylinder being spaced from the barrel to form a port therebetween,said cylinder having a lateral flange for limiting inward movement ofthe cylinder and predetermining the size of the port between saidcylinder and barrel, a piston operating in said cylinder and barrel, anda packing ring carried by the piston and arranged behind said port whenthe piston is in retracted position.

3. A- device of the class described comprising a casing divided by anintegral wall into a reservoir and a barrel, a cylinder in alignmentwith said barrel to form a continuation thereof, said barrel andcylinder being spaced apart ,to form a port therebetween, and a pistonoperable in said cylinder and barrel.

4. A device of the class described comprising 4a casing divided by anintegral wall into a reservoir and a barrel, a cylinder `in alignmentwith said barrel to form a continuation thereof, said barrel andcylinder being spaced apart to formy a port therebetween, means forvarying the spacing between said barrelv and cylinder to vary the sizeof said ports, and a piston operable in said cylinder and barrel.

5. A device of the class described comprising a casing divided by anintegral wall into a reservoir and barrel, a cylinder in alignment withsaid barrel to form a continuation thereof, said barrel and cylinderbeing spaced apart to form a port ltherebetween, said cylinder having alateral flange exteriorly of the casing, means disposed between saidange and casing for predetermining the size of said port, and a pistonoperable in said barrel and cylinder.

6. A device of the class described comprising a cylinder, a pistontherein, means for urging the piston to return to idle position afterbeing moved, a disc secured to the end of the cylinder to form anabutment for,y the piston when in idle position and said disc beingformed with a groove and a boot having an end received in said groove.

7. A device of the class described comprising a cylinder adapted tocontain a liquid, a piston in said cylinder adapted to force f/theliquid therein forwardly of .the cylinder', a reservoir, said cylinderhaving a port communicating the reservoir and cylinder forwardly of thenormal retracted position of the piston, said piston having an annulargroove adjacent its forward pressure face, a rubber packing ringreceived in said groove, said groove being slightly wider than thepacking ring to induce rolling action of the ring during a predeterminedtravel of the piston, said ring being compressed between the piston andcylinder wall, and said packing ring being disposed slightly rearwardlyof said port and in the forward end of said groove when the piston is inits normal retracted position, and adapted to roll across said port asthe piston moves forward and to slide upon the cylinder walls afterpassing said port.

NIELS A. CI-IRIS'IENSEN.

